This invention relates generally as indicated to a fluid control valve with variable pressure gain, and more particularly, to an actuator control system which preserves the original high pressure gain of the control valve about the valve null region to meet actuator threshold requirements and reduces the pressure gain outside the valve null region. Such control valves are especially intended for use in reducing opposing forces between two or more separate, independent actuators attached to a single aircraft flight control system or the like.
It is common practice to provide flight control systems for aircraft with redundant flight control actuators so that in the event one of the actuators should fail or shut down, the systems are still capable of properly functioning using the remaining actuator or actuators. Opposing forces (hereinafter referred to as "fight forces") between such redundant flight control actuators have generally been controlled with the use of tandem, synchronized control valves, or mechanical or electrical detection and feed back correction of the force flight between actuators. However, most feed back concepts cannot be used for this purpose when two or more separate, independent actuators are used to control the movements of a single aircraft flight control surface in that cross-channel information regarding force flights cannot be shared between independent actuators.
One recognized way of reducing or controlling force fights between separate, independent actuators is to provide an orifice between the load control passages leading from the control valve to the actuator to reduce the pressure gain of the actuator control valve. This effectively reduces the stiffness of the control valve and thereby reduces actuator force fights. However, this also lowers the pressure gain about the valve null region, which has the undesirable effect of decreasing the ability of the control valve to move the actuator with very small input commands to meet actuator threshold requirements.